A lithium ion battery comprises a positive electrode, a negative electrode, a separator disposed therebetween, and a non-aqueous electrolyte. Widely known as the positive electrode active material included in the positive electrode, is a lithium-containing cobalt oxide such as LiwCoO2 (where w is a variable that changes according to charge and discharge of the battery (hereinafter, the same meaning shall apply)). A lithium-containing cobalt oxide has a high potential relative to lithium, is excellent in reliability, and is relatively easy to synthesize.
Meanwhile, a lithium-containing nickel oxide such as LiwNiO2 has recently been considered for use and thus been put into use as a positive electrode active material. Lithium ion batteries using a lithium-containing nickel oxide is anticipated for use as the respective power sources for electric vehicles, hybrid cars, power tools, energy storage, etc. Thus, the following proposals have been made to obtain batteries being excellent in durability, reliability, and input/output characteristics.
PTL 1 discloses a lithium-containing nickel oxide containing different elements such as Co, Al, and Mn. According to PTL 1, such a lithium-containing nickel oxide has poor reactivity with a non-aqueous electrolyte, and its use as a positive electrode active material enables reduction in internal resistance of a lithium ion battery.
PTL 2 discloses a lithium ion battery having a positive electrode which includes: lithium nickel cobalt manganese oxide; and lithium carbonate having an average particle size of 5 to 30 μm. According to PTL 2, by mixing lithium carbonate having an average particle size of 5 to 30 μm, together with lithium nickel cobalt manganese oxide, both materials can be mixed evenly, resulting in improved reliability at times of overcharge.
[Citation List]
[Patent Literatures]
[PTL 1] Japanese Laid-Open Patent Publication No. 2006-127955
[PTL 2] Japanese Laid-Open Patent Publication No. 2008-181830